The present application proposes a program of studies organized around four broad issues dealing with the clinical, cognitive, functional, and neurophysiological significance of electrodermal activity and prepulse inhibition (PPI) of the startle eyeblink reflex. The four issues involve testing predictions derived from a vulnerability stress model of schizophrenia. The first (clinical) issue is whether anomalies in tonic electrodermal activity index a "transient intermediate state" that precedes symptomatic episodes in vulnerable individuals. The second (cognitive) issue is whether PPI can index both automatic and controlled cognitive processes when tested in the investigator's "attention-to-prepulse" paradigm. The third (functional) issue concerns whether PPI reflects a sensory inhibition process, while phasic electrodermal responses reflect sensory intake. A fourth (neurophysiological) issue addresses whether brain structural abnormalities are related to electrodermal and PPI anomalies in schizophrenia. These four issues will be tested in randomly selected college students, those selected to be putatively "at-risk" and in schizophrenic outpatients.